Monthly Archive December 7, 2020

28. Sharpening knife:

The shapes of computer gongs are different, and it is often necessary to grind all kinds of knives. When all kinds of forming knives are worn, they also need to be grinded. To achieve the following several percentages, a usable knife 1 can be grinded. The four corners of the tool should be the same height 2. Point a is higher than point D. the front (face) of tool 3 is higher than the back, that is, there is a certain back angle.

29. Over cutting check:

Overcutting is a common problem in MasterCAM. Be careful. Overcutting may occur in the process of multi curved surface opening, smooth knife, cutting path trimming, shape and groove digging, even if the parameter setting and stereogram of chest are correct, some are software errors. The main inspection method is to simulate the cutter path once again, and check repeatedly in the top view and side view. The tool path without inspection is not allowed to be used. In the process of contour milling, if the position of the lower tool is not selected properly, it will be over cut, which can be avoided by changing the lower tool position.

30. Milling direction:

Computer gongs are generally downmilling, unlike milling machine reverse milling, because the rigidity of computer gongs is better, it is not easy to let the cutter, the back clearance is small, milling shape or inner groove are left compensation. When processing symmetrical shapes, the tool path can not be mirrored, otherwise the processing effect will be bad on the side where the mirror passes. In order to communicate with the operator of the machine tool, the program paper should include 1) program name 2. Tool size and length 3. Tool path method 4. Machining allowance 5. Rough or smooth knife 6. Drawing file name 18. Graphic management Computer drawings should be properly classified and managed. It is better to create a catalog for a product and give a specific name for each part. For example, the name of the Copper drawing is A10, the name of the back die drawing can be a10c, the name of the front die drawing is a10cav, and the name of the loose Copper drawing is a10s1. 19. Format conversion between different softwares: communication with AutoCAD, the version above mastcam7 can read the DWG file directly, and the version lower than 7 can be converted to DXF format in AutoCAD. Other cam software such as cimtron, Pro / E, UG can be converted to IGS format.

31. DNC usage:

After the completion of the program, after checking, no problem can be copied to the DNC computer for actual processing. There are two ways to copy the program: one is to copy from disk; the other is to transmit it through LAN. Then start DNC software, find the program to run, and press enter.

32. Coordinate system:

There are three kinds, mechanical coordinate system, machining coordinate system and temporary coordinate system. In the mechanical coordinate system, the mechanical zero point is a reference point on the machine. After each power on, the zero point is determined after the zero point is returned to zero. The position of the mechanical zero point is determined by the machinery factory and should not be changed. The machining coordinate system is used for workpiece processing, which is the sub coordinate system of the mechanical coordinate system. Take a point in the mechanical coordinate system (generally the center point of the workpiece) as the coordinate origin, record the mechanical coordinate value of this point as the origin of the machining coordinate series, and then set the machining coordinate system. Temporary coordinate system: reset each point as the coordinate origin at any time. There are also three coordinate values corresponding to coordinate values: mechanical coordinate value, machining coordinate value and temporary coordinate value (also called relative coordinate value)

33. Common filter values:

The commonly used filtration values are 0.001 ~ 0.02, and the filtration radius r = 0.1 ~ 0.5. The larger the rough cutting path, the smaller the smooth surface path, the larger the surface radius and the smaller the larger the surface radius. Filtering can effectively reduce the program capacity and make the tool feed smoother, but if it is too large, the machining accuracy will be affected.

20. Common problems encountered in the die after processing:

The cutting tool should be made of the same material as that of the large one. The back die drawing is usually made of Copper drawing, which is made by reducing the material level plus PL surface, pillow position and the original body. If the material level is relatively uniform, negative material level can be directly reserved in the processing information, but pl (parting surface), pillow position and impact surface can not shrink the material level. At this time, you can first correct these surfaces by a material level or draw a section. One of the problems encountered by the original body department is that the ball knife can not clear the sharp angle. At this time, the flat knife can be used to process the sharp angle of the curved surface. For example, if the inlay section is used, the back mold is divided into the hidden frame and the core. When adding the Tibetan section, pay attention to the empty knife several times, otherwise the frame will have a slope, the upper edge is accurate, and the lower side is small, so it is difficult to match the mold. Especially for the deeper frame, we must pay attention to this problem, and the smooth frame knife should be new and good And choose a larger knife. If the core is too high, you can turn it over to process the frame, and then assemble it into the frame, and then process the shape. Sometimes there is a branch mouth. Be careful not to over cut. When using a ball knife to polish the shape, you must protect the edge steps. In order to facilitate the matching mode, the frame size can be smaller than the overall dimension of the core-0.02/s, and the tolerance and step distance of the core optical knife can be slightly larger, the tolerance is 0.01 ~ 0.03, and the feed is 0.2 ~ 0.5.

21. Problems in bulk copper processing:

Sometimes it is difficult to process the whole copper male, there is a dead angle that cannot be processed, or it is difficult to process. If the required tool is too long or too small, it can be considered to divide another copper male. Sometimes, it is necessary to clear the angle clearing copper male. However, it is not difficult to process this kind of copper male. However, it is necessary to make sure the deviation of flame time and check the benchmark.

22. Processing of thin disk copper male:

This kind of copper male is easy to be opened during processing. A new knife should be used. The knife should be small and the feed should not be too large. When processing, the length a should be set correctly, but D should be left with a large allowance (such as 1.0 mm) and then walk on both sides. Each time, the depth h = 0.2 ~ 1. The depth feed should not be too much, nor should it be moved around the knife, but should be divided into two sides.

23. Direction of left and right parts and one out two parts:

Sometimes a set of mold will produce two parts, for the left and right parts, the graphics can be produced by mirror. If two identical parts are produced, the figure must be balanced or rotated in XY, and must not be mirrored. Be careful not to reverse the direction.

24. CNC machining direction:

The four guide bolt holes of the die are not completely symmetrical, and one of them is asymmetric. Therefore, it is not clear when processing the front and rear dies. There is a benchmark on each template. When the front and rear dies are closed, they must be based on the datum, especially on the original die. When drawing, pay attention to the direction. The direction of the copper male is consistent with that of the front view (top view), the direction of the core of the family and the frame of the Tibetan family is the same as that of the copper male, while the direction of the front model is opposite. Some decorative lines such as grooves or boss on the surface are not easy to process because they are relatively narrow. For the groove, we generally avoid the groove empty, that is, milling deeper, and then add a loose male to make the sink surface. Generally, the boss can only be made into a loose joint separately, and the large copper male can not be made, so as to ensure the quality.

25. Fitting tolerance of mould and product:

A set of products usually has several or more than ten parts. The main matching dimensions of these parts are guaranteed by computer gong processing. It is very important to select reasonable tolerance, especially some product design drawings do not consider the matching problem. For the fit of bottom and surface shell, the shape is no doubt 0-0 fit, and the positioning is guaranteed by the support mouth. The tolerance of concave and convex support is generally 0.1 mm, single side. The shape of the accessories on the large body, such as transparent mirror, is 0.1 ~ 0.2 smaller than the size of the large body. The shape of the movable parts on the large body, such as buttons, is 0.1 ~ 0.5 smaller than that of the large body. The surface shape of the accessories on the big body should be consistent with the surface shape of the large body, and it can come down from the surface of the body.

26. Draft angle (draft angle)

Plastic mold must be made to the mold slope, otherwise it will be scratched. If the drawing does not indicate, you can consult with the mold maker. The mold angle is generally 0.5 ~ 3 degrees. If the etched mold, the mold angle should be larger, 2 ~ 5 degrees, depending on the thickness of the etch.

27. Cutting problem:

Most of the time, when the blade is just milled, the cutting amount is relatively large, which is easy to cause the knife to break and snap. At this time, you can first open the lower cutter position, or lift the knife away, or cut the knife outside the material in the daytime. In short, we should fully consider this problem. When the processing capacity is relatively large, the knife clip is too long and the knife is too small. It is easy to happen when the processing amount is relatively large, especially when there are more concentration feed. For example, if the smooth side depth h = 50 mm and the diameter is 3 / 4 cutter, we can process it in 25 mm twice, which is not easy to happen. If the tool holder is too long, the length of the tool installation is very important for processing. It should be as short as possible. Beginners can easily ignore this problem. The clamping length of the tool must be marked on the program paper. It is easy to grab the knife when turning the corner. The solution is to clean the corner with a smaller knife layer by layer, and then change the large knife to smooth the side. For the semicircular groove with diameter 8 as shown in the figure, if it is directly processed with R4 cutter, the cutting position is easy to grab the knife. The solutions are: (1) use R3 to scan the tool path; (2) use R3 to roughen first, and finally use R4 knife to clear the angle.

A number of years engaged in CNC processing experience, today to share with you.

1. The speed of white steel knife should not be too fast.
2. Copper roughing less white steel knife, more use flying knife or alloy knife.
3. When the workpiece is too high, it should be sliced with different length of knife.
4. After roughening with a big knife, use a small knife to remove the remaining material to ensure that the allowance is consistent.
5. The plane should be processed with flat bottom cutter and less ball cutter to reduce the processing time.
6. When the copper worker cleans the angle, first check the size of R on the angle, and then determine how large the ball knife is used.
7. The four corners of the calibration plane should be smooth.
8. If the slope is an integer, use the slope cutter to process, such as pipe position.
9. Before each process, think about the remaining allowance after the previous process, so as to avoid empty tool or excessive machining
10. Try to take simple cutting path, such as shape, grooving, single side, less walking around the same height.
11. When taking wcut, if you can walk finish, don’t go rough.
12. When the shape of the light knife is smooth, first rough and then fine. When the workpiece is too high, polish the edge first and then the bottom.
13. Set tolerance reasonably to balance machining accuracy and computer calculation time. The tolerance is set to 1 / 5 of the allowance for roughening and 0.01 for smooth knife.
14. Do more procedures to reduce the time of empty knife. Think more and reduce the chance of making mistakes. Make more auxiliary lines and auxiliary surfaces to improve the processing condition.
15. Establish a sense of responsibility and check each parameter carefully to avoid rework.
16. For CNC processing, diligent in learning, good at thinking, continuous progress. When milling non flat surface, use ball cutter more, use less end knife, do not be afraid to connect knife; small knife angle cleaning, big knife finishing; don’t be afraid of patching, proper patching can improve the processing speed and beautify the processing effect.
17. High hardness of blank material:

Better up milling, lower hardness of blank material: better forward milling, better machine tool precision, good rigidity, finish machining: more suitable for forward milling, vice versa, more suitable for finish machining of inner corner of parts by up milling. It is strongly recommended to use forward milling. Rough machining: reverse milling is better, finish machining is better: down milling is better, tool material toughness is good, hardness is low: it is more suitable for rough machining (large cutting amount processing), tool material toughness is poor, hardness is high: it is more suitable for finishing (small cutting amount processing).

Copper processing method

Before writing the cutter path, after the three-dimensional drawing is finished, the graphic center should be moved to the coordinate origin, and the highest point should be moved to Z = 0 before machining. The copper male spark position can process negative reservation. Before processing, it is also necessary to check whether the clamping direction of the workpiece is the same as the graphic direction in the computer, whether the arrangement in the mold is correct, whether the fixture hinders the processing, and whether the direction of the front and rear dies match. Also check whether the tools you use are complete, and check the benchmark in the calibration table. Matters needing attention in copper processing: for the determination of spark position, the reserved amount of young male (i.e. fine male) is 0.05 ~ 0.15 and coarse male is 0.2 ~ 0.5. The specific spark position can be determined by the mold maker. Copper public has no dead corner that cannot be processed. Whether it is necessary to dismantle one more loose one. Generally, the cutter path of copper processing is as follows: big knife (flat knife) roughening – small knife (flat knife) angle clearing – ා 0; smooth knife uses spherical knife to smooth curved surface. In general, teachers use a flat knife instead of a ball knife. After a big knife, they use a small knife to make a rough cut. Then they use a large ball knife to smooth the surface, and then use a small ball knife to smooth the surface. It is not easy to use a small knife to process the dead angle that the big knife can’t pass for some small angles. It is advisable to limit the range of the knife’s travel so as to avoid too many empty knives. Copper, especially Yougong, requires high precision. The tolerance is generally 0.005 ~ 0.02 and the step distance is 0.05 ~ 0.3. When the copper is exposed to be thick, the tool passing position of the ball cutter position should be reserved, that is, the copper male shape should be opened to a depth of a knife radius. In general, the copper worker must have three datum planes when calibrating three surfaces (upper, lower, left and right). Copper material is easy to process. The feed speed and rotation speed can be faster. When roughing, the machining allowance is 0.2 ~ 0.5. Depending on the size of the workpiece, the machining allowance is large, so the cutting can be fast and the efficiency can be improved. Note: the brackets are the parameters of high-speed steel knife for steel roughening, and the above cutting speed refers to that the required profile f = 300 ~ 500, and the steel smooth cutter f = 50 ~ 200.

19. Problems of front die opening:

First of all, rotate the Copper drawing 180o in the front view or side view to turn it into the front mold drawing, and of course, add the pillow position and PL surface. If the original body needs to be reserved, do not use the mirror body method to change the Copper drawing into the front model drawing, which may be wrong (when the X direction and Y direction of the Copper drawing are asymmetric). There are two difficulties in front mold processing: the material is relatively hard; the front mold can not be easily welded and wrong. The principle of using a knife for roughening the front die is similar to that of a copper tool. However, a large knife should be used as far as possible for the front die, rather than a too small knife. It is easy to snap the knife. Generally, the handle () is used for roughening, and the round nose knife is also used for the smooth knife. Because this kind of knife is large and powerful, there is usually a problem when processing the front die with parting surface The parting surface should be accurate because of the impact of the machine, and the cavity should be left 0.2 ~ 0.5 machining allowance (reserved for spark). In this way, the surface of the die cavity can be corrected by 0.2 ~ 0.5 towards the positive direction, and the machining allowance can be set to 0 when the face is writing the tool path. When the front die is roughened or polished, it is usually necessary to limit the cutting range. Remember that the range you set is the range of the tool center, not the range of the tool boundary, not the range of the tool processing, but a larger tool radius. Front die opening is commonly used